sedimentary

Chert (Jasper variety)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Hardness: 6
Color: Reddish-brown, tan, and cream
Luster: Dull to waxy

Identified May 9, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 on Mohs scale; Color: Reddish-brown, tan, and cream; Luster: Dull to waxy; Crystal Structure: Cryptocrystalline; Cleavage: None (conchoidal fracture).

Formation & geological history

Formed through the accumulation of silica-rich organic remains or chemical precipitation in sedimentary environments; often found in nodules within limestone or as bedded deposits.

Uses & applications

Historically used for stone tools due to sharp edges; currently used for lapidary work, jewelry, and landscaping gravel.

Geological facts

Chert was one of the most important minerals for prehistoric humans because its conchoidal fracture creates extremely sharp edges for spear points and knives.

Field identification & locations

Identify by its hardness (cannot be scratched by a steel knife) and its smooth, shell-like (conchoidal) fracture surfaces. Commonly found in riverbeds and sedimentary outcrops.